It is known in the prior art to construct large rectangular liquid storage tanks which are made by assembling together a plurality of square plastic panels. These panels usually have peripheral flanges shaped to interfit with each other and with a gasket or elastomer material at the interfitting flanges to prevent leakage.
Two principal uses for such large tanks are: (a) on the roofs of buildings to hold water for fire protection or to insure uniform water pressure in the plumbing system of the building and (b) for storage of water in dry climates where an adequate supply of rain water and/or well water may not be available for much of the year.
In particular, this invention is directed to an improvement in large panel type water storage tank such as that disclosed in Wakana et al U.S. Pat. No. 4,050,605 (assigned to Bridgestone Tire Company Limited of Tokyo, Japan), the entire disclosure of which is hereby incorporated by reference and will be referred to hereinafter as "Wakana et al".
In the Wakana et al patent, long metal tie rods extend across the tank to prevent the sidewalls of the tank from bulging outwardly due to the pressure exerted by the water in the tank when it is full or partly full.
Experience has shown that such metal tie rods (usually stainless steel) do not work out well in practice due at least partly to (a) unequal coefficients of expansion between the non-metal glass reinforced plastic (GRP) panels and the metal tie rods and (b) corrosion of the stainless steel fittings, particularly where welded.